engine GMC YUKON DENALI 2003 Workshop Manual

Q: Am I likely to stall when going downhill?
A: It’s much more likely to happen going uphill. But if it
happens going downhill, here’s what
to do.
Stop your vehicle by applying the regular brakes.
Apply the parking brake.
Shift to PARK (P) and, while still braking, restart the
Shift back to a low gear, release the parking brake,
If the engine won’t start, get out and get help.
engine.
and
drive straight down.
Driving Across an Incline
Sooner or later, an off-road trail will probably go across
the incline
of a hill. If this happens, you have to
decide whether
to try to drive across the incline. Here
are some things
to consider:
A hill that can be driven straight up or down may be
too steep to drive across. When you go straight up
or down a
hill, the length of the wheel base (the
distance from the front wheels
to the rear wheels)
reduces the likelihood the vehicle will tumble end
over end. But when you drive across an incline,
the much more narrow track width (the distance
between the left and right wheels) may not prevent
the vehicle from tilting and rolling over.
Also,
driving across an incline puts more weight on the
downhill wheels. This could cause a downhill
slide or a rollover.
Surface conditions can be a problem when you
drive across a hill.
Loose gravel, muddy spots,
or even wet grass can cause your tires
to slip
sideways, downhill.
If the vehicle slips sideways,
it can hit something that will trip
it (a rock, a rut, etc.)
and roll over.
Hidden obstacles can make the steepness of the
incline even worse. If you drive across a rock
with the uphill wheels, or
if the downhill wheels
drop into a rut or depression, your vehicle can tilt
even more.
For reasons like these, you need to decide carefully
whether to try to drive across an incline. Just because
the trail goes across the incline doesn’t mean you
have to drive it. The last vehicle to try it might have
rolled over.
4-24

Driving in Water
Heavy rain can mean flash flooding, and flood waters
demand extreme caution.
Find out how deep the water
is before you drive through
it. If it’s deep enough to cover your wheel hubs, axles
or exhaust pipe, don’t try
it - you probably won’t
get through. Also, water that deep can damage your
axle and other vehicle parts.
If the water isn’t too deep, drive slowly through it. At
faster speeds, water splashes on your ignition system
and your vehicle can stall. Stalling can also occur
if you
get your tailpipe under water. And, as long as your
tailpipe is under water, you’ll never be able to start your
engine. When you go through water, remember that
when your brakes get wet, it may take you longer
to stop.
I
- - - - -ng through rushing water can be
dangerous. Deep water can sweep your vehicle
downstream and you and your passengers
i could drown. If it’s only shallow water, it can
still wash away the ground from under your
tires, and you could lose traction and roll the
vehicle over. Don’t drive through rushing water.
I I
See Driving in Rain and on Wet Roads on page 4-29 for
more information on driving through water.
After Off-Road Driving
Remove any brush or debris that has collected on the
underbody, chassis or under the hood. These
accumulations can be a fire hazard.
After operation in mud or sand, have the brake linings
cleaned and checked. These substances can cause
glazing and uneven braking. Check the body structure,
steering, suspension, wheels, tires and exhaust
system for damage.
Also, check the fuel lines and
cooling system for any leakage.
Your vehicle will require more frequent service due to
off-road use. Refer
to the Maintenance Schedule
for additional information.
4-27

Hydroplaning
Hydroplaning is dangerous. So much water can build up
under your tires that they can actually ride on the
water. This can happen
if the road is wet enough and
you’re going fast enough. When your vehicle is
hydroplaning, it has little or no contact with the road.
Hydroplaning doesn’t happen often. But it can
if
your tires do not have much tread or if the pressure in
one or more is low. It can happen
if a lot of water is
standing on the road. If you can see reflections
from trees, telephone poles or other vehicles, and
raindrops “dimple” the water’s surface, there could be
hydroplaning.
Hydroplaning usually happens at higher speeds. There
just isn’t a hard and fast rule about hydroplaning.
The best advice is to slow down when
it is raining.
Driving Through Deep Standing Water
Notice: If you drive too quickly through deep
puddles or standing water, water can come
in
through your engine’s air intake and badly damage
your engine. Never drive through water that
is
slightly lower than the underbody of your vehicle. If
you can’t avoid deep puddles or standing water,
drive through them very slowly.
Drivhg Through Flowing Water
~~
I
Flowing or rushing water creates strong forces.
If you try to drive through flowing water, as you
might at a low water crossing, your vehicle can
be carried away.
As little as six inches of
flowing water can carry away a smaller vehicle.
If this happens, you and other vehicle
occupants could drown. Don’t ignore police
warning signs, and otherwise be very cautious
about trying to drive through flowing water.
Some Other Rainy Weather Tips
Turn on your low-beam headlamps - not just your
parking lamps
- to help make you more visible to
others.
* Besides slowing down, allow some extra following
distance. And be especially careful when you
pass another vehicle. Allow yourself more clear
room ahead, and be prepared to have your
view restricted by road spray.
* Have good tires with proper tread depth. See Tires
on page 5-55.
4-31

Once you are moving on the freeway, make certain you
allow a reasonable following distance. Expect
to
move slightly slower at night.
When you want to leave the freeway, move
to the
proper lane well in advance.
If you miss your exit, do
not, under any circumstances,
stop and back up. Drive
on
to the next exit.
The exit ramp can be curved, sometimes quite sharply.
The exit speed is usually posted.
Reduce your speed according
to your speedometer, not
to your sense of motion. After driving for any distance
at higher speeds, you may tend to think you are
going slower than you actually are.
Before Leaving on a Long Trip
Make sure you’re ready. Try to be well rested. If you
must start when you’re not fresh
- such as after a day’s
work
- don’t plan to make too many miles that first
part of the journey. Wear comfortable clothing and shoes
you can easily drive in.
Is your vehicle ready for a long trip? If you keep it
serviced and maintained, it’s ready
to go. If it needs
service, have it done before starting out. Of course,
you’ll find experienced and able service experts
in dealerships all across North America. They’ll be
ready and willing
to help if you need it. dere
are some things you can check before a trip:
e
e
e
e e
e
e
Windshield Washer Fluid: Is the reservior full? Are
all windows clean inside and outside?
Wiper Blades: Are they in good shape?
Fuel, Engine Oil, Other Fluids: Have you checked
all levels?
Lamps: Are they all working? Are the lenses clean?
Tires: They are vitally important
to a safe,
trouble-free trip.
Is the tread good enough for
long-distance driving? Are the tires all inflated to the
recommended pressure?
Weather Forecasts: What’s the weather outlook
along your route? Should you delay your trip a
short time
to avoid a major storm system?
Maps:
Do you have up-to-date maps?
4-34

Highway Hypnosis
Is there actually such a condition as “highway
hypnosis”? Or is it just plain falling asleep at the wheel?
Call it highway hypnosis, lack
of awareness, or
whatever.
There is something about an easy stretch of road with
the same scenery, along with the hum of the tires on the
road, the drone of the engine, and the rush of the
wind against the vehicle that can make you sleepy. Don’t
let
it happen to you! If it does, your vehicle can leave
the road in less than a second, and you could crash and
be injured.
What can you do about highway hypnosis? First, be
aware that
it can happen.
Then here are some tips:
Make sure your vehicle is well ventilated, with a
Keep your eyes moving. Scan the road ahead and
comfortably
cool interior.
to the sides. Check your mirrors and your
instruments frequently.
If you get sleepy, pull off the road into a rest,
service or parking area and take a nap, get some
exercise, or both. For safety, treat drowsiness
on the highway as an emergency.
Hill and Mountain Roads
Driving on steep hills or mountains is different from
driving in flat or rolling terrain.
If you drive regularly in steep country, or if you’re
planning to visit there, here are some tips that can make
your trips safer and more enjoyable. See Operating
Your All- Wheel-Drive Vehicle
Off Paved Roads on
page
4- 16 for information about driving off-road.
4-35

0 Keep your vehicle in good shape. Check all fluid
levels and also the brakes, tires, cooling system
and transmission. These parts can work hard
on mountain roads.
Know how to go down hills. The most important
thing to know is this: let your engine do some of
the slowing down. Shift
to a lower gear when you go
down a steep or long hill.
_. you c tt : ft down, your brakes could get
so hot that they wouldn’t work well. You would
then have poor braking or even none going down
a hill. You could crash. Shift down to let
your engine assist your brakes on
a steep
downhill slope.
L,ast,,,, ,ownh,,, NEUTrlmL (N) or with the
ignition
off is dangerous. Your brakes will have
to do all the work
of slowing down. They could
get so hot that they wouldn’t work well. You
would then have poor braking
or even none
going down
a hill. You could crash. Always
have your engine running and your vehicle in
gear when you go downhill.
Know how to go uphill. You may want to shift down
to a lower gear. The lower gears help cool your
engine and transmission, and you can climb the
hill better.
Stay in your own lane when driving on two-lane
roads in hills or mountains. Don’t swing wide or
cut across the center of the road. Drive at speeds
that let you stay in your own lane.
As you go over the top of a hill, be alert. There
could be something in your lane, like a stalled car or
an accident.
4-36

You can run the engine to keep warm, but be careful.
L..Jw can trap exhaust gases ,..der your
vehicle. This can cause deadly CO (carbon
monoxide) gas to get inside.
CO could
overcome you and kill you. You can’t see
it or
smell it, so you might not know it is in your
vehicle. Clear away snow from around the base of your vehicle, especially any that is
blocking your exhaust pipe. And check around
again from time to time to be sure snow
doesn’t collect there.
Open a window just
a little on the side of the
vehicle that’s away from the wind. This will
help keep
CO out.
Run your engine only
as long as you must. This saves
fuel. When
you run the engine, make it go a little
faster than just idle. That
is, push the accelerator
slightly. This uses less fuel for the heat that
you get and
it keeps the battery charged. You will need a
well-charged battery
to restart the vehicle, and possibly
for signaling later
on with your headlamps. Let the
heater run for
a while.
4-40

Then, shut the engine off and close the window almost
all the way
to preserve the heat. Start the engine
again and repeat this only when you feel really
uncomfortable from the cold. But do it as little as
possible. Preserve the fuel as long
as you can. Po help
keep warm, you can get out of the vehicle and do
some fairly vigorous exercises every half hour or
so until
help comes.
If You Are Stuck: In Sand, Mud, Ice
or Snow
In order to free your vehicle when it is stuck, you will
need
to spin the wheels, but you don’t want to spin your
wheels
too fast. The method known as “rocking” can
help you get
out when you’re stuck, but you must
use caution.
you let yeerr tires spin at high speed, -..zy
can explode, and you or others could be
injured.
And, the transmission or other parts of
the vehicle can overheat. That could cause an
engine compartment fire or other damage.
When you’re stuck, spin the wheels as little as possible. Don’t spin the wheels above
35 mph
(55 km/h) as shown on the speedometer.
Nofice: Spinning your wheels can destroy parts of
your vehicle
as well as the tires. If you spin the
wheels too fast while shifting your transaxle back
and forth, you can destroy your transaxle. See
“Rocking Your Vehicle
To Get It Out.”
For information about using tire chains on your vehicle,
see
Tire Chains on page 5-62.
4-41

To identify the trailering capacity for your vehicle, you
should read the information in “Weight of the Trailer” that
appears later in this section.
If yours was built with trailering options, as many are,
it’s ready for heavier trailers. But trailering is different
than just driving your vehicle by itself. Trailering means
changes in handling, durability and fuel economy.
Successful, safe trailering takes correct equipment, and
it has
to be used properly.
That’s the reason for this part. In it are many time-tested,
important trailering tips and safety rules. Many of
these are important for your safety and that of your
passengers.
So please read this section carefully before
you pull a trailer.
0
0
If You Do Decide To Pull A Trailer
If you do, here are some important points:
There are many different laws, including speed limit
restrictions, having
to do with trailering. Make sure
your rig will be legal, not only where you live
but also where you’ll be driving.
A good source for
this information can be state or provincial police. Consider using a
sway control
if your trailer will
weigh
5,000 Ibs. (2 270 kg) or less. You should
always use a sway control
if your trailer will weigh
more than
5,000 Ibs. (2 270 kg). You can ask a
hitch dealer about sway controls.
Don’t tow a trailer at all during the first
500 miles
(800 km) your new vehicle is driven. Your engine,
axle or other parts could be damaged.
Then, during the first
500 miles (800 km) that you
tow a trailer, don’t drive over
50 mph (80 km/h)
and don’t make starts at full throttle. This helps your
engine and other parts of your vehicle wear in at
the heavier loads.
You can tow in
DRIVE (D). You may want to shift
the transmission
to THIRD (3) or, if necessary, a
lower gear selection
if the transmission shifts
too often (e.g., under heavy loads and/or hilly
conditions). See “Tow/Haul Mode” under Towing
a
Trailer on page 4-47.
Three important considerations have to do with weight:
0 the weight of the trailer,
the weight of the trailer tongue
0 and the weight on your vehicle’s tires.
4-48

Tow/Haul Mode
The tow/haul feature assists when pulling a heavy trailer
or a large or heavy load. The purpose
of the tow/haul
mode
is to:
Reduce the frequency and improve the predictability
of transmission shifts when pulling a heavy trailer or
a large or heavy load.
Provide the same solid shift feel when pulling a
heavy trailer or a large or heavy load as when
the vehicle is unloaded.
Improve control of vehicle speed while requiring
less throttle pedal activity when pulling a heavy
trailer or a large or heavy load.
Your vehicle is provided with a button at the end of the
shift lever which when pressed enables tow/haul.
When the button is pressed, a light on the instrument
panel will illuminate
to indicate that tow/haul has
been selected. Tow/haul may be turned
off by pressing
the button again, at which time the indicator light on
the instrument panel will turn off. The vehicle will
automatically turn off tow/haul every time it is started. Tow/haul
is designed
to be most effective when the
vehicle and trailer combined weight is at least
75 percent
of the vehicle’s Gross Combination Weight Rating
(GCWR). See Weight
of the Trailer later in this section.
Tovdhaul is mcst useful wder the f~l!~~ing driving
conditions:
When pulling a heavy trailer or a large or heavy
0 When pulling a heavy trailer or a large or heavy
load through rolling terrain.
load
in stop and go traffic.
When pulling a heavy trailer or a large or heavy
load in busy parking
lots where improved low
speed control of the vehicle is desired.
Operating the vehicle in tow/haul when lightly loaded or
with no trailer at all will not cause damage. However,
there is no benefit
to the selection of tow/haul when the
vehicle is unloaded. Such a selection when unloaded may result in unpleasant engine and transmission driving
characteristics and reduced fuel economy. Tow/haul
is recommended only when pulling a heavy trailer or a
large or heavy load.
4-49